One approach to the study of higher mental processes in man involves the evaluation of changes in electrical brain activity and behavior produced by psychotropic drugs. The proposed research involves the study of two centrally acting drugs, having antagonistic effects on attention and arousal processes, on a slow electrical potential of the human brain called "contingent negative variation" or CNV. One substance is amphetamine, a stimulant of the central nervous system (CNS) and the other is chlorpromazine, a CNS depressant. CNV is related to attention and arousal functions. The neurophysiological genesis of CNV includes the brain stem reticular formation, a site known to be activated by amphetamine and depressed by chlorpromazine. The intent of the proposed experiments is to examine the effects of amphetamine and chlorpromazine on CNV magnitude in the context of experiments having dissociable task requirements for attention and arousal processes. These findings are expected to strengthen the view that CNV is a sensitive measure of higher mental processes. This program of research involves the two psychotropic drugs and CNV in the context of specific experiments on sensory evoked potentials, monosynaptic reflex activity, motor potentials, and sleep deprivation. It is expected to yield information about attention and arousal processes that might help in understanding these impaired functions in schizophrenics and to develop experimental techniques which can be directly applied to the study of CNV in schizophrenics.